The filter whose parameters are to be retrieved. Must
be one of GL_CONVOLUTION_1D, GL_CONVOLUTION_2D, or GL_SEPARABLE_2D.

pname

The parameter to be retrieved. Must be one of GL_CONVOLUTION_BORDER_MODE,
GL_CONVOLUTION_BORDER_COLOR, GL_CONVOLUTION_FILTER_SCALE, GL_CONVOLUTION_FILTER_BIAS,
GL_CONVOLUTION_FORMAT, GL_CONVOLUTION_WIDTH, GL_CONVOLUTION_HEIGHT, GL_MAX_CONVOLUTION_WIDTH,
or GL_MAX_CONVOLUTION_HEIGHT.